Modern stepped variable speed transmissions such as automated transmissions, planetary automatic transmissions and double clutch transmissions can be operated both in a manual mode as well as in an automatic mode. In the manual mode, shiftings can be directly initiated by the driver, for example when the driver manually deflects a gearshift lever provided for this purpose in order to upshift or downshift. In the automatic mode, however, shiftings are initiated automatically by determining current vehicle-, road- and driver-specific operating parameters and initiating shiftings on the basis of gear change characteristics or shifting characteristics. These operating parameters can include the current traveling speed, the current driving acceleration, the current engine speed, the current engine torque, the current vehicle mass, the current road inclination (uphill, flat, downhill), the current tractive resistance and the current driver's intention (the performance requirements of the driver, or a cruise control system or Tempomat™). The current operating parameters can either be measured directly, or be calculated from measured values. Likewise, the respective current gradient can be determined and used for shift control. For example, the current driver's intention can be determined by means of an associated characteristic curve from the position of the accelerator pedals, measurable via a potentiometer. In addition, the calculable rate of change of the accelerator pedal position over time, or in other words the control speed, can also be used.
Based on current operating parameters and if applicable, also on their gradients, the shift control or automatic stepped variable speed transmissions delivers good results in most operating conditions, including high dynamic performance, low fuel consumption and a high level of shifting and driving comfort. There are frequently late or awkward shiftings in the thrust operation however, especially in the transition between different road gradients and driving resistances, since conventional methods of shift control do not, or do not sufficiently, take into account the topography of the stretch of road that lies ahead of the motor vehicle.
So, for example, a transition on a stretch of road with a downgrade is frequently detected too late in a section of the road having a greater downgrade based on current operating parameters, so that the motor vehicle is already accelerated under the effect of an increased downhill force and a thrust downshift needed to limit the traveling speed is delayed and therefore is initiated at an increased traveling speed. On the other hand, a thrust downshift may not infrequently be unnecessarily initiated due to a currently greater downgrade in the road, if the stretch of road with a downgrade then transitions back to a section of the road having a lesser downgrade in a short distance, which would then again entail a thrust upshift.
Similarly, in a transition from a downgrade into a level stretch, the leveling off of the downgrade in question is frequently detected too late due to current operating parameters, so that a thrust upshift, which is appropriate in this instance, is initiated too late, whereby the momentum of the motor vehicle (potential and kinetic energy) is inadequately exploited and a transition into traction mode is necessary earlier than is possible. On the other hand, a thrust upshift may also be unnecessarily initiated due to a currently lesser downgrade in the road if the stretch of road with a downgrade then transitions back to a section of the road having a greater downgrade in a short distance, which would then again entail a thrust downshift.
In order to further improve the shifting behavior of automatic stepped variable speed transmissions, some methods and devices have already been suggested, which provide for the compiling of topographic data that relates to a stretch of road that lies ahead of the motor vehicle, in particular of the elevation profile, and taking that profile into consideration during the shift control of an automatic stepped variable speed transmission.
Thus, in the document DE 101 42 274 A1, a method for controlling and/or regulating the vehicle speed is suggested, in which, in connection with an operation of a brake control system (Bremsomat) and/or a cruise control system (Tempomat™), the target speed of the Bremsomat or Tempomat is dynamically modified. The known method provides that entry into an incline as well as in a leveling off of the downgrade is detected through the evaluation of current operating parameters, their gradients and information pertaining to the stretch of road such as, in particular, topography data, and in these cases, the target speed of the Bremsomat or the Tempomat is detected in a timely manner.
In the document DE 10 2006 001 818 A1, a method and a device for driver assistance in the driving operation of a commercial vehicle are described, for which the topography data that pertains to the stretch of road that lies ahead of the motor vehicle on the travel section can be retrieved from a memory and evaluated with the aid of a computer when adjusting the driving operation components, in particular when the transmission control sets a gear of the transmission. The topography data can be stored in the form of an elevation profile or a gradient profile for the respective travel section.
Finally, a method and a device for controlling and/or regulating an automatic system of a motor vehicle are known from document DE 10 2005 050 753 A1, for which data is collected in order to detect a stretch of road that lies ahead of the motor vehicle and combined into a tractive resistance profile of a motor vehicle. The tractive resistance profile that is calculated should be used inter alia in an automatic transmission, to set an appropriate gear ratio in order to manage the stretch of road that lies ahead of the motor vehicle.
The methods and devices known from the prior art provide useful approaches for improving the shifting behavior of automatic stepped variable speed transmissions. Specific information about how control commands are derived from topography data that pertains to the stretch of road that lies ahead of the motor vehicle such as the elevation profile, the gradient profile or the tractive resistance profile, and how those commands are implemented in the transmission control cannot be found in the above mentioned documents.